The present invention relates to self-developing photographic apparatus, in general, and to such apparatus utilizing photographic film units having a rupturable developer-fluid-containing pod attached to one end thereof, in particular.
Photographic apparatus of the self-developing type are well-known in the art and generally include film advancing means for engaging and moving an exposed film unit out of its exposure position within a light-tight film cassette and into engagement with a pair of pressure-applying, fluid spreading members such as a pair of longitudinally extending parallel rollers spaced a predetermined distance from one another. The film unit includes a pod, or container, of processing composition (developer liquid) having a sealed, rearwardly facing discharge end which is parallel to a leading edge of the film unit. The rollers are positioned to engage the leading end of the pod on the advancing film unit and subsequently generate sufficient pressure within the processing composition to rupture the seal and spread the contents thereof across a photosensitive layer of the film unit to initiate the formation of a visible image within the film unit while simultaneously advancing the film unit out of the photographic apparatus.
A plurality of film units are stacked within a box in the form of a light-tight cassette that includes a molded housing such that each of said film units may be sequentially moved into the exposure position and then out of the photographic apparatus after being moved into a gap between said composition spreading, pressure applying rollers by said film advancing means. The film unit is located in the exposure position within the cassette with its leading edge parallel with the axes of the rollers and the film-advancing structure must be constructed such that minimum changes in this parallelism occur while the film unit is being advanced into the bite of the rollers in order to insure uniform distribution of spreading processing composition.
In molding some types of light-tight film cassette housings, it is essential that a draft angle be incorporated within the cassette in order to facilitate mold-member removal after the molding process is complete. This draft angle causes the cross-section of the cassette housing at the end where the film unit exits to be slightly larger than the cassette housing cross-section end remote from said exit end. Normal exposed-film unit advancing practice in self-developing cameras consists of advancing the film unit out of the exposure station and into the bite of the composition-spreading rollers by applying an asymmetrical force at that edge of the film unit remote from the cassette opening, in the direction of preferred film unit movement. However, the application of such a film unit-moving asymmetrical force causes the film unit to rotate about an axis normal to the direction of preferred film unit movement and to thereby destroy the above-mentioned desirable parallelism between the leading edge of the film unit and the axes of the rollers and thereby interfere with the ability of the spread system to uniformly spread the processing composition of a self-developing film unit. In addition, in processing composition spread systems of the type that include a pair of spaced-apart annular flow-controlling recesses or grooves in one of a pair of adjacent composition spreading rollers for the purpose of precluding the "red-framing" effect in accordance with the teachings of U.S. Pat. No. 3,647,441 to BACHELDER, it is essential that these annular grooves continuously span the side edges of the visible image to be formed in an advancing film unit in order to insure that "red-framing" does not occur. Any significant rotation of the film unit relative to the spread system prior to processing composition spreading would reduce the effectiveness of these composition-flow-controlling grooves.
Several arrangements have been employed in the past to avoid this incomplete processing composition spreading problem. In one arrangement, described in U.S. Pat. No. 3,854,809 to DRISCOLL, a tapered gap is established between a pair of processing composition spreading rollers to compensate for the incomplete spreading that would otherwise be caused by film unit canting when the film unit is moved into the bite of a pair of rollers by an asymmetrical force-providing actuator. In another arrangement described in U.S. Pat. No. 3,829,871 to GOLD, pressure-applying rollers are mounted with the bite or longitudinally extending gap being positioned at an acute angle with respect to the leading edge of the film unit located within the camera in position for exposure. This aforementioned acute angle is equal to the same number of degrees that the film unit is subsequently canted during its movement out of its exposure position and into the bite of the processing composition spreading rollers. In yet another arrangement described in U.S. Pat. No. 3,864,703 to GOLD, camming structure is provided for returning the film unit to a position where its leading edge is once again parallel to the bite of a roller pair gap after being moved from its exposure position by an asymmetrical force.
It is a primary object of the present invention, therefore, to provide photographic apparatus for processing a film unit of the self-developing type such that a leading edge of the film unit is aligned in parallel with a longitudinally extending gap defined by a pair of pressure-applying members and maintained in said alignment during film unit processing movement.
Another object of the present invention is to provide a light-tight film cassette and a plurality of stacked film units therein wherein rotational movement of said film units within the cassette about an axis normal to the direction of preferred film unit movement is precluded when an assymetrical force is applied to an edge of said film unit during film unit processing movement.
A further object of the present invention is to provide a light-tight film cassette with non-parallel side walls for precluding rotational movement of film units within said cassette about an axis parallel to the direction of preferred film unit movement when an asymmetrical force is applied to an edge of said film units during film unit processing movement.
Other objects and advantages of my invention will be made readily apparent by referring to the preferred embodiments thereof described in detail below.